Anticoagulation is vital in hemodialysis (HD) to maintain adequate dialysis. The use of anticoagulating agent is, however, limited in patients with high risk of bleeding. To evaluate the effect of Fractionated heparin(FH) in HD patients with high risk of bleeding, 19 patients(10 major surgery, 7 gastric bleeding, 1 each of renal cyst bleeding and pericardial effusion) were included in this study. Four consecutive HD sessions using single intravenous injection of FH(0.2ml in patients with body weight 40-70kg and 0.3ml for over 70kg) followed by 4 consecutive HD sessions with low dose or no heparin(LH) were performed in 9 patients and in reverse order in 10 patients. Major hemorrhagic episodes were recorded and pre and post HD body weight, blood pressure, activated partial thromboplastin time(APTT), hemoglobin(Hb), hematocrit (Hct), and platelet count(Plt) were obtained. Clots in venous air trap and/or artificial kidney was given scores: 0, none; 1, fibrin ring; 2, fibrin ring requiring saline flush; 3, complete obstruction. The color of dialyser after completion of dialysis was given the following scores: 0, pale; 1, pale pink; 2, pink. Time of compressing needling site to prevent vascular access bleeding was recorded. Hypotensive episode was not observed during HD. Recurrence of gastric bleeding in 3 patients(5 episodes with FH and 4 episodes with Control) and renal cyst bleeding(1 episode with FH) were observed during the study period. No bleeding complications were observed in the other 15 patients. No significant differences in pre-and post APTT, Hb, Hct, and Plt were observed between FH and Control. Significantly fewer coagulation episodes in venous air traps and/or artificial kidneys was observed during HD with FH than Control(0.07+/-0.19 vs. 0.79+/-0.91). No significant difference was observed in hemodialyser color at the end of dialysis and time of compressing needling site between FH and Control. Tubing system was changed due to complete obstruction of extracorporeal system in 4 episodes in 3 patients in Control group, but not in FH group. In conclusion, Fraxiparine was effective in preventing coagulation in the extracorporeal circulation and did not increase bleeding complications during HD in high risk patients and is recommended for use in HD patients with high risk of bleeding.